The present invention relates generally to an optical sensor and a method of operation thereof and in particular to a method of enhancing sensor accuracy.
Optical sensors are commonly used for a variety of functions including detecting skewed or double picked notes within the note transport mechanism of an Automated Teller Machine.
A variety of different prior art detectors have been utilized to detect note skew in ATMs. These include both electromechanical and optical detectors. However, they all have certain features in common. In particular, they all rely on a pair of sensors, each of which is located at a predetermined position along the transport path within the ATM. Also as the detector is arranged to determine skew perpendicular to the direction of travel along the transport path, both sensors and light sources must be located within the transport path, thus making assembly and serviceability of the detectors difficult. For example, cables must be laid into both sides of the transport path to connect to the sensors.
In addition, changes in LED power and sensor sensitivity throughout the lifetime of a sensor have also caused problems when attempting to use optical sensors for note detection in an ATM.
A further problem with the use of optical sensors is the large variation in the opacity of notes used today. Also, some bank notes have relatively transparent windows. With prior art optical sensors these windows are seen as holes.